These are either the Mangrove rivulus or the Yucatan gambusia, it's nearly impossible to tell the difference. The Mangrove and Liberty mollies are more easily recogniseable due to their red or yellow tails
@Mr Gharial Thank you for the correction. I was unfortunately mistaken in thinking these were also mollies, for which I'm sorry. I unfortunately cannot change the title anymore.
@KevinB It's absolutely no worries. As I said, the four livebearers on the mudflats are nearly impossible to tell apart, so unless you know that little factoid about two of them having yellow tails, you won't know which is which.
Actually, I know that little factoid and I still don't really know
